El Castillo is in the center of Chichen Itza. Created by the Maya Civilization for their God, Kukulkan, the Yucatec Maya Feathered Serpent deity.
Thousands of people visit this temple during the spring and fall equinox to watch as the shadowed serpent appears down the four corners of the pyramid.
Mexican government discovered a second temple hidden below El Castillo in the 1930's.